1. Field of the Disclosure
Embodiments of the present invention relate to a touch panel, and more particularly, to a touch panel attached to a top surface of a panel, and a display device using the same.
2. Discussion of the Related Art
Touch screens are a type of input device that is included in display devices such as Liquid Crystal Displays (LCDs), Field Emission Displays (FEDs), Plasma Display Panel (PDPs), Electroluminescent Displays (ELDs), and Electrophoretic Display (EPDs), and allows a user to input information by directly touching a screen with a finger, a pen or the like while a user looks at the screen of the display device.
Touch panels may be configured in various types depending on an arrangement position in a display device.
First, the touch panel may be formed in an on-cell type in which the touch panel is attached to a top surface of a panel.
Second, the touch panel may be formed in an in-cell type in which two electrodes of the touch panel are formed in a same layer of a thin film transistor (TFT) substrate of a liquid crystal panel.
Third, the touch panel may be formed in a hybrid type in which one of two electrodes of the touch panel is formed in the TFT substrate of the liquid crystal panel and the other is formed at the top surface of a color filter substrate.
Fourth, the touch panel may be formed in an add-on type in which a film including a touch electrode is attached to a tempered glass, or a touch electrode is formed in a tempered glass itself.
The in-cell type touch panel and the hybrid type touch panel may be generally applied to a liquid crystal display, but the on-cell type touch panel and the add-on type touch panel may be attached to a top surface of a panel of a display device irrespective of the type of the display device.
FIG. 1 is an exemplary view illustrating the exterior of a display device according to the related art. FIG. 2 is an exemplary view illustrating a cross section of a bezel in a display device provided with an add-on type touch panel according to the related art. FIG. 3 is an exemplary view illustrating an arrangement structure of driving electrodes and receiving electrodes in a touch panel according to the related art
In case of the related art, since a research and development of product was been mainly focused on a function of a touch panel, a bezel corresponding to a non-display area of panel or display device has not been studied actively. Thus, as shown in FIG. 1(a), a width of bezel is formed largely.
Recently, in addition to the research and development in technical and functional aspects, a design aspect of a product is being mainly researched and studied. As shown in 1(b), there has been provided a display device having a bezel′ whose width is relatively reduced in comparison to the related art.
As shown in FIG. 1, a bezel corresponds to a circumferential area, that is, a non-display area on which an image is not displayed. As shown in FIG. 1, a bezel may be a non-display area when a case is mounted thereon, or a bezel itself may be a non-display area. Generally, a width of bezel in a display device depends on a width of bezel in a panel, whereby a method of reducing the bezel of the panel has been studied actively.
Meanwhile, according as a function of the display device varies, the display device is developed to satisfy a trend of increasing a display area on which an image is displayed.
Especially, the display device is designed in such a manner that a width of bezel is reduced so as to create an effect of increasing a display area under a condition that a size of display area is kept intact.
However, the display device according to the related art has limitations on reduction of width in the bezel.
First, in case of a panel with a touch panel, in order to reduce a width of bezel, there is an attempt to decrease a glass cutting area and a sensor expand area provided to sense a touch on a display area of the touch panel, as well as a routing area provided with a touch electrode line.
However, if a size of the bezel is reduced below a preset level, it is difficult to obtain a margin of the routing area, sensor expand area, and glass cutting area.
A cross section of a routing area included in a bezel of an on-cell type display device in which a touch panel 30 is attached to a top surface of a panel 10 by UV resin 20 will be shown in FIG. 2.
That is, in case of a related art touch panel, as shown in FIG. 2, metal routing lines 34 are formed on an lower surface of a black matrix 32 attached to a surface of a glass substrate 31, wherein the metal routing lines 34 are provided in parallel, and are connected to touch electrodes. Also, a sensor expand electrode 33, which expands from the touch electrode, is formed in parallel to the metal routing lines 34.
According to the above structure, a width of the routing area, that is, a width of bezel is reduced by reducing a width of the metal routing line 34, to thereby reduce an pitch between each of the metal routing lines 34.
However, if the metal routing line 34 is reduced in width, a resistance is increased, whereby touch sensitivity might be degraded. Also, a range of reducing the width of the metal routing line 34 is limited. According as the interval between each of the metal routing lines 34 is reduced, the touch sensitivity may be degraded due to noise occurring between each of the metal routing lines 34.
Thus, a method of reducing the width of the metal routing line 34 and the interval between each of the metal routing lines 34 has limitations.
Second, in case of a related art touch panel 30 comprising five driving electrodes TX1 to TX5 which receive driving pulses, and six receiving electrodes RX1 to RX6 which receive sensing signals, as shown in FIG. 3(a), there may be thirty touch coordinates 36.
In order to explain touch sensitivity at each of the touch coordinates 36, as shown in an expanded square part ‘x’ of FIG. 3(a), the driving electrode TX3 and receiving electrode RX4 cross each other in a capacitive type touch panel. Generally, touch sensitivity at a crossing region of the driving electrode and receiving electrode (hereinafter, referred to as ‘crossing region’, u) is greater than touch sensitivity at a region (u′) where the driving electrode is adjacent to the receiving electrode.
Accordingly, as shown in FIG. 3(a), the related art touch panel is provided in such a manner that the crossing region of the driving electrode and receiving electrode, that is, the region of the touch coordinates 36 is included in an active area A/A (display area) on which an image is displayed, and a bezel is formed in the circumferential area. That is, the driving electrode and receiving electrode crossing each other are formed on the touch panel, but the region which is not included in the active area A/A corresponds to an over scan area, wherein the over scan area is formed in the bezel. That is, according as the over scan area is increased in size, the bezel is increased in width.
In order to reduce the width of bezel, the related art touch panel may be provided with the over scan area which is cut, as shown in FIG. 3(b).
That is, the number of touch coordinates 36′ in the active area A/A of the touch panel 30′ shown in FIG. 3(b) is the same as the number of touch coordinates 36 in the active area A/A of the touch panel 30 shown in FIG. 3(a). However, unlike the over scan area of the touch panel 30 shown in FIG. 3(a), the over scan area formed in the bezel of the touch panel 30′ shown in FIG. 3(b) is cut to be smaller, whereby an occupying size of the over scan area is reduced, and thus the width of bezel is reduced.
As shown in an expanded square part ‘y’ of FIG. 3(b), the crossing regions of the driving electrode and receiving electrode and the regions where the driving electrode is adjacent to the receiving electrode in the outermost area of the touch panel are smaller in number than those in the other areas of the touch panel.
Thus, as described above, on the assumption that thirty of the touch coordinates 36 are formed in the touch panel 30′ by the five driving electrodes and six receiving electrodes, touch sensitivity in eighteen of the touch coordinates in the outermost area of the active area A/A is relatively lower than touch sensitivity in twelve of the touch coordinates in the other areas of the active area A/A.
As a result, there are limitations on reduction of over scan area formed in the circumference of the touch panel.